In the past stone slabs forming an exterior facade of buildings have been secured to the building structure utilizing adhesives. However, some building codes now require stone slabs be mechanically coupled to structures. Previously known mechanical systems to mount stone slabs have not been satisfactory.
For example, U.S. Pat. No. 4,060,951 to Gere teaches a mechanical mounting system in which a plug hole is drilled into the edge of a slab to intersect at right angles with a bolt hole drilled into the rear of the slab. A bolt in the bolt hole is threaded into a plug in the plug hole. With the bolt secured to the structure, the bolt and plug co-operate to mechanically mount the slab to the structure. In Gere location of the plug hole on the edge of the slab is disadvantageous as difficult to access to drill the hole and, particularly in an assembled facade, to access the hole as may be necessary to change a slab. Moreover, the location of the plug hole and bolt hole near an edge is disadvantageous as being a location where the slab may most readily fracture thus substantially reducing the forces which the mechanical mounting may withstand, as determined by the nature of the stone slab being used and particularly its thickness.
U.S. Pat. No. 3,786,605 to Winfrey teaches a mechanical system for mounting slabs by slots cut into the top and bottom ends of the slabs into which pins may vertically extend supported on metal supports extending horizontally from the structure. In Winfrey location of the slots along the edges of the block reduces the ultimate strength of the system.
U.S. Pat. No. 4,531,338 to Donalt provides two studs which extend at an angle with respect to each other, diverging away from each other, into a slab with the rear ends of the studs crossing rearward of the slab. By encasing the crossing rear ends in enclosed pockets filled with epoxy, the rear ends of the studs effectively form a closed loop secured to the structure. Donalt has the disadvantage of being complex to assemble and relying on the epoxy bonding to maintain the joint. Further Donalt limits its structure to being a poured concrete slab. Donalt is not practical on steel structures.